There is really a couple of main reasons Portugal was not included.
Its biggest claim to fame is its exploration and colonization which, in deed, opened many possibilities to Spain and in turn the rest of Europe. But I believe when looking for major civilizations to include they look for a distinct and prolific culture, a strongly developed, and society and government, and some sort of international influence (which aside from Portugal's exploration it was quite lacking compared to most, if not all the civs included). Also I believe there to be a bit more to being considered great than just exploration and in turn exploiting the indigenous populations of Africa, the Americas, and Asia (to a smaller degree). No doubt that virtually all the European nations who were explorers are guilty of this, but these also had strong culture and distinction with quite large populations. (At least larger than Portugal).
So if you were to include Portugal I would say to include Spain first since they are, not totally, but in a few ways similar, and Spain having considerably more influence in the long run and many more people than Portugal. Including both Spain and Portugal and not say, the Celts, would be like including Norway and Sweden, but not the Turks. But I can understand your Nationalistic pride and thats very good and healthy, but there are simply too many other civs that were left out as well.